Letter to the Editor: Prevalence of Self-Reported Cannabis Use among Patients at a Supportive Care Clinic in a Tertiary Cancer Center

Methods

In this retrospective study, we reviewed the charts of 120 random patients at first consultation evaluated at the supportive clinic at The University of Texas MD Anderson Cancer Center from January 1 to December 31, 2020. Eligible patients were 18 years or older and had a diagnosis of cancer. The institutional review board approved the study, and a waiver of informed consent was granted. During each visit, all patients are asked about the use of any cannabinoid product and the answer is documented in the chart.

Statistical analyses were carried out in IBM^® SPSS^® Statistics, Version 26. The Student's t test, the Mann–Whitney U test, chi-squared test, and Fisher's exact test were used for comparisons between groups. The 95% Clopper–Pearson confidence interval (CI) was calculated as needed. A p value <0.05 was considered statistically significant.

Results

Eleven patients self-reported using cannabis products at the time of the visit for a prevalence (95% CI) of 9.2% (4.7–15.8%). Results are presented in Table 1. The only differences between patients who used cannabis products and those who did not were patients using cannabis were predominantly male, were more often taking selective serotonin reuptake inhibitors/serotonin and norepinephrine reuptake inhibitors, and in those taking opioids, the morphine equivalent daily dose was higher.

Discussion

We found that about 1 in 10 patients self-reported using cannabis products during their first consultation to a supportive clinic at a tertiary cancer center. Interestingly, our group previously found that 37% (44/119) of patients on long-term opioids for cancer pain (who underwent random urine drug testing in the same setting) screened positive for cannabis. ¹ This finding suggests that asking routinely for cannabis use may result in underreporting. Only in 2019 did the state of Texas add “terminal cancer” among the qualifying conditions that can be treated with low-dose tetrahydrocannabinol and patients may be less open to report cannabis use in states where it is considered illegal. ²

Knowing about cannabis use is important because oncological patients are frequently receiving centrally acting drugs such as opioids, hypnotics, or antidepressants, and there are risks for serious pharmacodynamic and pharmacokinetic interactions. ³ There is a considerable financial cost for these agents and patients can benefit from a discussion with their physician. It is possible that patients would be more willing to report cannabis use once more rapport has been established during follow-up. More research is needed to determine the best modality to assess the utilization of these agents.

Our study has several limitations. Data were collected retrospectively, the sample is small, and it was conducted in a single tertiary medical center in a state that has only recently approved the use of cannabis in patients with terminal cancer, which make our findings not easily extrapolable to other medical settings. Further prospective investigations in different settings are warranted.

Authors' Contributions

P.S.B. contributed to conceptualization, methodology, acquisition of data, formal analysis, and original draft preparation. A.C. and A.B. were involved in methodology and acquisition of the data. B.F. carried out methodology and formal analysis. K.T. and E.B. were in charge of conceptualization, supervision, reviewing, and editing.